Polymer blends made from polycarbonate and acrylonitrile-butadiene-styrene copolymer (ABS) have long been known. Their full range of properties, comprising high heat resistance, good (low-temperature) strength and improved processing properties in comparison to pure polycarbonate, make PC+ABS blends particularly suitable for interior and exterior automotive applications, for example.
These blends may be made flame resistant with halogen-based and in particular with halogen-free flame retardants. Flame-resistant PC+ABS blends, particularly those based on halogen-free phosphoric acid esters as flame retardants, have become established in electrical and information technology applications over the last 15 years.
For the processing, i.e., the shaping, of molding compositions, which for most of the afore-mentioned applications is carried out by injection molding, good melt flow is essential. Improved melt flow allows greater design freedom, the production of larger molded parts with few gate marks (i.e., few weld lines, which generally indicate a mechanical weak spot in the molded parts), or a reduction in the processing temperature, through which
On the other hand, the consumer articles produced from the molding compositions are expected to display mechanical and thermal ruggedness, i.e., good strength and heat resistance, but also in particular a good resistance to chemicals, greases and oils and household cleaning products.
A simultaneous improvement in processing behavior and chemical resistance, with sustained heat resistance, is not generally achievable. For example, although the flowability of PC+ABS blends may be improved by reducing the average molecular weight of the polycarbonate used, the chemical resistance of the material suffers severely as a consequence. The chemical resistance may be increased by using special ABS components, but the flowability of the molding composition generally suffers as a consequence. In PC+ABS blends that have been treated with phosphoric acid esters to make them flame resistant, the flowability may be improved by increasing the amount of flame retardant, but the heat resistance in particular suffers as a consequence.
The object of the present invention was thus to provide PC+ABS compositions which are characterized by improved melt flow combined with improved chemical resistance, with sustained heat resistance.